Portable pre-cast fireplace



P v5, 1967 P. A. KREIDER 3,339,540

PORTABLE PRE- CAST FIREPLACE F'iled Sept. 1965 2 Sheets-Sheet 1 I INVENTOR. P5752 A. KEEVDEQ p 1-967 P. A. KREIDER 3,339,540

PORTABLE PRE"CAST FIREPLACE Filed Sept. '7, 1965 2 Sheets-Sheet 2 A? TO/QNE Y United States Patent 3,339,540 PORTABLE PRE-CAST FIREPLACE Peter A. Kreider, 1307 Denise Court, Brea, Calif. 92621 Filed Sept. 7, 1965, Ser. No. 485,400 10 Claims. (Cl. 126-121) ABSTRACT OF THE DISCLOSURE A portable fireplace that can be easily and quickly assembled from two to three prefabricated components for use indoors, in a patio, or the like.

' As is well known, the conventional brick or stone fireplace is an expensive installation, even when included at the time a residence is built. Normally, the cost of installing a fireplace after erection of a residence, is, of course, substantially greater than if it had been built originally as a part thereof. This expense has discouraged the installation of fireplaces, whether it be at the time the residence is constructed or thereafter. Also, when such conventional fireplace installations have been made in the past, many of them have been primarily decorative, and oftentimes most inefiicient as a heat-producing unit.

A primary object in devising the present invention is to provide an inexpensive fireplace that can be easily and quickly assembled from either two to three prefabricated portable components, and when assembled, comprises a fireplace which is predominantly concrete.

Another object of the invention is to furnish a fireplace that is attractive in appearance, requires no elaborate plant facilities for the production of the components thereof and is highly eflicient in operation.

Yet another object of the invention is to supply a portable fireplace, the components of which can be fabricated from inexpensive, standard, commercially available materials.

These and other objects and advantages of the invention will become apparent from the following description of several forms thereof, and from the accompanying drawings illustrating the same, in which:

FIGURE 1 is a perspective view of a first form of the portable, precast fireplace;

FIGURE 2 is a front elevational view of the fireplace shown in FIGURE 1;

FIGURE 3 is a vertical cross-sectional view of the fireplace shown in FIGURE 2, taken on the line 3-3 thereof;

FIGURE 4 is a front elevational view of a second form of the fireplace;

FIGURE 5 is a vertical cross-sectional view of the second form of the invention, taken on the line 55 of FIGURE 4;

FIGURE 6 is a front elevational view of a third form of the device;

FIGURE 7 is a top plan view of the third form of the fireplace;

FIGURE 8 is a vertical cross-sectional view of a fourth form of the invention; and

FIGURE 9 is a perspective view of a cam-guided firescreen door hinge, utilized with the fireplace.

With continued reference to the drawings for the general arrangement of the first form of the invention, it will be seen in FIGURE 1 to include a bottle-shaped shell A, the front of which is vertically truncated to define a semielliptical opening 10 therein. In the fabrication of the shell A, a screen 12 is included, which is bent or otherwise formed to conform with the shape of the shell, to which screen a number of laterally spaced reinforcing bars 14 are aifixed, together with a number of stitfeners 3,339,540 Patented Sept. 5, 1967 18 is composed of the following components by volume:

Rocklite sand 1.0 Large granule Perlite 2.0 Small granule Perlite 3.0 Diatomaceous earth 3.0 Glass fiber strands (1" loose) 2.0 Asbestos fibers /2 Plastic Portland cement 3 /2 Water, add to reach plastering or casting mix as required. Air entrainment liquid, 4 /2 liquid ounces per cubic yard of the above mixture.

When formed or plastered to define the shell A, the density of this concrete mixture is approximately 60 lbs. per cubic foot after drying for a week, which is far lighter than the 150 lbs. weight per cubic foot normally encountered in regular concrete. Also, it has been found that the above described lightweight concrete has a much higher heat insulation value and higher heat resistance than that of regular concrete weighing approximately 150 lbs. per cubic foot.

The upper end of shell A develops into a neck 20 that receives a conventional metal flue piep 22, as best shown in FIGURE 3. Below the neck 20, the shell A curves downwardly and outwardly to terminate in a flat lower edge 24 which rests on the upper surface of a circular slab 26 formed of the high temperature, lightweight concrete previously described. An opening 28 is formed in the rear portion thereof, also as shown in FIGURE 3.

The circumferential edge 30 of slab 26 tapers downwardly and inwardly and is received within the upper portion of a shallow dish-shaped member 32 that may be fabricated from metal or other suitable rigid material. The member 32 is supported on a second inverted dish-shaped member 34 and attached thereto by welding beads 36, or other suitable fastening means. A number of elongate longitudinally extending openings 38 are formed in member 32 that are in vertical spaced relationship. Air from the ambient atmosphere can flow rearwardly through openings 38 into a confined space 40 defined by the member 32 and slab 26, with the air from the confined space passing upwardly through the opening 28.

A metal firewall 42 is disposed within the confines of the shell A, and is in abutting contact with the upper surface of slab 26. The firewall 42-is connected to the stiffeners 16 by conventional means (not shown). The firewall 42 includes a lower vertical portion 44, the upper part of which develops into an upwardly and forwardly extending portion 46. Portion 46 in turn develops into a rearwardly extending section 48 that abuts against the upper, rea-r interior surface of shell A, as shown in FIGURE 3.

An opening 50 is formed in the rear portion of the shell A below the extension 48, and a screen 52 is mounted therein. Opening 50 communicates with a confined space 54 that is defined by the rear part of shell A, firewall 42, the rear part of slab 26, and extension 48. A

v part of a hinge 56 is mounted on extension 48, which downwardly and rearwardly from the interior of the shell 3 A, as best seen in FIGURE 3. By manipulation of the rod 60, any one of the teeth 62 can be caused to selectively engage the U-shaped member 64 to support the damper 58 at a desired position and control the burning of wood or other fuel (not shown) in the fireplace.

An eye 66 is mounted on the forward surface of the section 46 of firewall 42, and pivotally supports a hook 68. A grate 70 (FIGURE 3) that is pivotally supported by a pin 72 which engages an eye 74 projecting forwardly from the lower part of the firewall 42. The grate 70 is' held in a substantially horizontal position by one or more lags 76 which project downwardly from the forward portion thereof. A loop 78 is provided on the forward portion of the grate 70, which is removably engaged by the hook 68 to support the grate in an upwardly and forwardly extending position and permit the upper surface of the slab 26 within the confines of the shell A to be swept or otherwise cleaned without the usual grate or andirons obstructions.

The opening in shell A is semielliptical or other symmetrical configuration, and is closed by two fire screen doors 80 that are of substantially the same shape. Each of the doors 80 is defined by a rigid frame 82 of such size that each door can fit within the confines of the opening 10, with the adjoining portions of the doors being in vertical abutting contact, as shown in FIGURE 1. The frames 82 each support a suitable screen or perforated sheet material 84.

Two journal blocks 86 are positioned inside shell A in the opening 10 adjacent the slab 26 and afiixed by conventional means to upwardly extending interior surfaces 87 of the shell as shown in FIGURE 9. Each journal block 86, as shown in FIGURE 9, has a bore 88 extending therethrough. Two bolts 90 are mounted in tapped vertical bores 91 formed in the journal blocks 86 with the inwardly disposed portion of the bolts projecting into the bores 88. Two rods 92 are slidably and rotatably supported in bores 88. J-shaped slots 94 are formed in each rod 92 that engage the inner ends of the bolts 90. The outer ends of the rods 92 turn upward, as can best be seen in FIGURES 1, 2, and 3, and serve to support a handle 96.

The lower outer extremity 98 of each of the doors 80 (FIGURE 9) are welded or otherwise afiixed to one of the rods 92. When either of the rods 92 is moved outwardly by use of the handle 96, the door 80 associated with that particular handle is first moved outwardly from the confines of the opening 10, and then, due to the action of one of the bolts 90 and J-shaped slots 94, the door is pivoted outwardly away from the adjacently disposed door, and clear of opening 10. When one of the rods 92 is moved inwardly, the door 80 associated therewith is first pivoted towards the other door, and then due to the cooperation of one of the bolts 90 with one of the J-shaped slots 94, the door being moved is oriented to slide into the confines of the opening 10.

The use and operation of the invention are most simple. The elements comprising the portable fireplace are first assembled in the position shown in FIGURE 3, and connected to the flue pipe 22. Fuel is then placed within the confines of the shell A to rest on the grate 70. The handles 96 are then utilized to close the doors 80 to the position shown in FIGURES 1 and 2. As the fuel (not shown) burns, the hot gases from the combustion thereof rise in the shell A to flow upwardly past the damper 58 and discharge into the ambient atmosphere through the flue pipe 22. Normally, the fiue pipe will be connected to a chimney (not shown) that acts as an extension thereof. As the fuel (not shown) burns, the firewall 42 is heated. Heat is radiated and transferred from the firewall 42 to heat the cool air in the confined space 54, with this heated air flowing outwardly through openings 50 into the room in which the portable fireplace is positioned, to circulate in the room and heat the same. As hot air rises in the confined space 54 to discharge through openings 50, cold air from the room flows through the opening 38, confined space 40, and opening 28 to replace the heated air in the confined space 54 as the heated air moves upwardly in the manner described. The cool air flowing upwardly through space 54 keeps the rear portion of the fireplace cool, and permits the fireplace to be positioned adjacent the walls in the corner of a room without damage thereto. The removal of ashes from the first form of the device is easily achieved by pivoting the grate upwarly and rearwardly where it is supported by the book 68. The slab 26, as may be seen in FIGURE 3, serves as a support for an upright 97 from which fireplace implements 99 are removably supported.

A second form of the fireplace is shown in FIGURES 4 and 5. This form of the fireplace includes a number of elements that are common to the first form, and these common elements are identified in the drawings by the same numerals previously used in identifying the first form, but to which a prime has been added.

In the second form of the invention, the shell A is provided with a neck 100 that is defined by walls 102, the exterior surfaces of which taper downwardly and inwardly, as can best be seen in FIGURE 5. The shell A rests on the upper surface of a slab 26' that may be of any desired shape, and an opening 28' is formed therein. The slab 26 rests on the upper surface of a rectangular concrete block 104 through which an L-shaped air passage 106 extends. The forward end of the air passage 106 is covered by a screen 108. The rear part of the air passage 106 turns upwardly and is in vertical alignment with the opening 28'. The second form of the invention is formed from the same materials used in the first form thereof, and operates in the same manner. Accordingly, a detailed description of the operation of the second form of the device need not be given.

A third form B of the portable fireplace is shown in FIGURES 6 and 7, that may be positioned in a comer of a room 110 that is partially defined by two walls 112 and 114. The third form B includes a pre-cast concrete base 116, the forward face of which is preferably covered with a decorative material 118. Two openings are formed in that portion of the base 116 covered with the decorative material 118. Panels 122 are positioned in openings 120, and are provided with louvers 124. Two air passages 126 extend rearwardly in base 116, and merge to provide a connecting passage 128, as best seen in FIG- URE 7. Two vertical openings 130 are formed in base 116 that are in communication with air passages 126. Also, a number of vertical openings 132 are formed in the rear portion of base 116 that lead upwardly from the connecting passage 128.

A prefabricated shell 134 forms a part of the third form of the device, which is fabricated from the same materials used in the manufacture of shell A shown in the first form of the device. The shell 134 has two rearwardly and inwardly tapering side walls 136 (FIGURE 7) that abut against the exterior surfaces of the walls 112 and 114. The side walls 136 are connected at their rear ends by a wall 138. A semielliptical opening 140 is formed in the forward portion of shell 134, which is normally closed by two doors 142, that are of the same structure as the doors 80 disclosed in the first form of the device.

The forward portion of the shell B is designated in the drawings by the numeral 144. A fire wall 146, having a back 148 and two side walls 150, is disposed inside the shell B, as shown in FIGURE 7. The side walls 150 of fire wall 146 cooperate with the interior surface of the shell B to define two confined spaces 152 that are in communication with the openings 130 in the base 116. The back 148 of fire wall 146, cooperates with the shell B to define a confined space 154 that is in communication with the openings 132 in the base 116. The confined spaces 152 and 154 are in communication with two openings 156 formed in the upper forward portion of the shell B, as can be seen in FIGURE 6. All forms of the portable fireplaces may include this feature if desired. Screens 158 are mounted in the openings 156. The upper portion of the shell B has an opening 160 that is connected to a flue pipe 162. The third form of the invention also includes a damper (not shown), of the same structure used in the first and second forms of the device.

The third form of the invention also includes a grate (not shown) and handles 164 for moving the doors 142. The structure of the doors 142 and the mechanism actuated by the handles 164, are the same structure as like parts described in connection with the second form of the device. When fuel is burned in the third form of the fireplace, air is heated, in the confined spaces 152 and 154 and rises therein to discharge through the openings 156 into the room in which the fireplace is situated to heat the same. To replace the hot air that moves upwardly in the confined spaces as previously described, cold air from the room flows through the louvers 124 and air passages 126 and 128 to pass upwardly through the openings 130 and 132 into the confined spaces 152 and 154.to be heated and then discharged through the openings 156. Due to cold air being heated in the confined spaces 152 and 154, only a slight amount of heat is transferred to that portion of the shell B in abutting contact with the walls 112 and 114. Accordingly, there is no danger of the portion of the shell B in contact with the walls 112 and 114 heating the same sufliciently to cause the walls to catch on fire or be charred.

A fourth form of the device is shown in FIGURE 8 that is adapted to be included as a part of the wall of a house C, or similar structure. The fireplace includes a precast concrete shell D having a back wall 166, top 168 and forward wall 170 in which an opening 172 is formed. A second opening 174 is formed in wall 170 that is of the same shape as the opening in the first form of the device, and this second opening normally is closed by a pair of doors 176. The doors 176 are of the same structure as the doors 80 previously described. The doors 176 may be pivoted to open and closed positions by the use, of handles 178 and associated mechanisms (not shown), that are of the same structure as the handles 96 illustrated in connection with the first form of the device.

The-fourth form of the device has two side walls 180 that are connected to the vertical ends of the back wall 166, top 168 and forward wall 170. The two side walls 180 support a transversely positioned pre-cast hearth 182 therebetween. As can be seen in FIGURE 8, the pre-cast shell D is supported on a base 184 that extends outwardly from the concrete foundation 186 and floor 188 supported thereby, which foundation and floor are a part of the house C. A wall 190 extends upwardly from top- 168 to the roof 192 of the house C.

An air passage 194 is defined between an upper surface of the base 184 and the hearth 182. A fire wall 196 is disposed inside the shell D, and includes an upwardly extending portion 198-and a substantially horizontal portion 200 at the'upper end thereof. A damper 202 of the same structure as described in the first form of the device, is mounted on the upper forward extremity of the firewall 196. The firewall 196 and the side walls 180, as well as back wall 166, cooperatively define an upwardly extend-- ing confined space 204" in the fourth form of the fireplace that is in communication with the air passage 194. The firewall 196 has an opening 206 formed in the upper portion thereof, from which a metallic tube 208 extends forwardly to the opening 172. A fireplace lighter 210 is provided in the fourth form of the device, which is connected to a tube 212 that extends to a source of gas. Flow of gas through the tube 212 is controlled by a valve 214, which is operated by a handle 216 that extends through the air passage 194. A flue pipe 218 is connected to an opening 220 formed in the top 168. The flue pipe 218 extends upwardly through the roof 192 of the house C.

- in which the fourth form of the device is situated is drawn through the air passage 194. The cold air flowing into the confined space 204 is subsequently heated.

The use and operation of the various forms of the device have previously been described in detail and need not be repeated.

Although the .present invention is fully capable of achieving the objects and providing the advantages hereinbefore mentioned, it is to be understood that it is merely illustrative of the presently preferred embodiment thereof and I do not mean to be limited to the details ofv construction herein shown and described, other than asdefined in the appended claims.

I claim:

1. A portable pre-cast fireplace, which includes:

(a) a base of noncombustible material through which a horizontal cool air passage extends that develops at the rear end thereof into an upwardly extending passage;

(b) a pre-cast shell of lightweight concrete of low heat conductivity and high temperature resistance that rests on said base, and inthe forward portion of which shell a symmetrical fireplace opening i formed, with the upper portion of said shell developing into a tubular neck that can be connected to a fiue pipe;

(c) a transversely positioned metallic firewall disposed in said shell that divides the interior thereof into a rear confined space that is in communication with said upwardly extending passage in said base and at least one warm air discharge opening formed in the upper rear portion of said shell, with the forward portion of said divided shell being utilized for the consumption of fuel;

(d) two abutting doors that fit within the confines of said fireplace opening;

(e) means for so movably supporting each of said doors that they can first be withdrawn from said opening and then pivoted in a direction to permit access to the interior of said shell;

(f) a grate supported from said firewall in said forward portion of said shell; and

(g) a damper adjustably supported from said firewall in said forward portion of said shell for regulating the draft to which fuel burning on said grate is subjected, which burning fuel heats said firewall to in turn heat said cool air entering said confined space from said passage, with the air heated in said confined space rising to pass from said warm air discharge opening, with said cool air as it rises and is heated in said confined space. serving to absorb substantially all the heat radiated thereto by said firewall and by so doing preventing any substantial heating of said shell rearwardly of said firewall.

2. A fireplace as defined in claim 1 wherein said base includes:

(h) a metallic disc-shaped member, in the forward portion of which at least one opening is formed;

(i) a slab of noncombustible material that rests in the upper interior portion of said disc-shaped member, which slab and member cooperatively define said horizontal air passage, with said upwardly extending passage being defined by an opening formed in I the rear portion of said slab; and

(j) means for supporting said disc-shaped member in a horizontal position at a desired elevation above a floor surface in a room in which said fireplace is located.

3. A fireplace as defined in claim 1, wherein said shell is of a bottle-shaped configuration and said fireplace opening is symmetrical in shape.

4. A fireplace as defined in claim 1, which further includes:

(h) means for pivotally supporting said grate from said firewall;

(i) at least one leg for supporting said grate in a substantially horizontal position when said leg rests on said base; and

(j) means afiixed to said firewall for removably holding said grate in an upwardly extending position to permit that portion of said base in said forward portion of said shell to be cleaned.

5. A fireplace as defined in claim 1, wherein said means for supporting each of said doors comprises:

(h) a journal block afiixed to said shell adjacent one of the lower outer extremities of said fireplace open- (i) an elongate member extending through said block to place an inner portion thereof in a bore that extends longitudinally through said block;

(j) a rod rotatably supported in said bore, which rod is rigidly affixed to one of said doors and has a J-shaped slot formed therein which movably engages said elongate member, with said slot being of such shape that said door must be moved out of said fireplace opening before said rod and door can be pivoted; and

(k) a handle on said rod for manually moving the same to place said door in an open or closed position relative to said fireplace opening.

6. A fireplace as defined in claim 1, wherein said base is formed from cast concrete and has a Hat horizontal upper surface, which fireplace further includes:

(h) a slab of noncombustible material that rests on said base and supports said shell, said slab having an opening formed therein that is in vertical alignment with said upwardly extending passage, with a portion of said slab extending forwardly from said base.

7. A portable pre-cast fireplace, which includes:

(a) a base of noncombustible material in which two rearwardly extending, laterally spaced air passages are formed that are in communication with a rearwardly positioned connecting passage, and in which base a plurality of vertically extending openings are formed that connect with said rearwardly extending passages and said connecting passage;

(b) a pre-cast shell of lightweight concrete of low heat conductivity and high temperature resistance, that rests on said base, with said shell having a fireplace Opening in the forward portion thereof, with the upper portion of said shell developing into a tubular neck that can be connected to a flue pipe;

() a transversely positioned metallic firewall disposed in said shell, which firewall includes a back and two side walls extending forwardly therefrom, with said firewall dividing the interior of said shell into a confined space that is in communication with said openings in said base, and a forward portion wherein fuel is consumed;

(d) two abutting doors that fit within the confines of said fireplace opening;

(e) means for so movably supporting said doors that each can first be withdrawn from said opening and then pivoted in a direction to permit access to the interior of said shell;

(f) a grate supported from said firewall in said forward portion of said shell; and

(g) a damper adjustably supported from said firewall in said forward portion of said shell for regulating the draft to which fuel burning on said grate is FRED R CK subjected, which fuel as it burns heats said firewall to in turn heat said air in said confined space, with said heated air in said confined space rising to pass from warm air discharge openings located in the upper forward portion of said shell, while cool air from a room in which said fireplace is situated is drawn into said confined space through said air passages and openings to replace said heated air and in turn be heated for discharge into said room.

8. A fireplace as defined in claim 7, which further includes:

(h) a decorating facing that covers the forward portion of said base; and

(i) two sets of louvers disposed in the forward extremities of said two air passages.

9. In combination with a building having a floor, walls and a roof supported by said walls, a fireplace which includes:

(a) a base disposed adjacent an edge of said floor and extending upwardly thereabove;

(b) a pre-cast concrete shell that rests on said base, which shell comprises a back, side walls extending forwardly from said back, and a forward portion in which a fireplace opening is defined, with said shell being partially disposed in an opening formed in one of said walls of said building, and with said shell also having an opening formed in the upper portion thereof to which a fiue pipe can be connected, which opening and flue pipe are disposed outside said build- (c) a transversely positioned slab that extends between said side walls at a desired elevation above said base, wtih said base and slab cooperatively defining a rearwardly extending air passage;

(d) a transversely positioned metallic firewall disposed in said shell that divides the interior thereof into a rearwardly disposed confined space that is in communication with said air passage;

(e) two abutting doors which fit within the confines I of said fireplace opening;

(f) means for so movably supporting said doors that each can first be withdrawn from said opening and then pivoted in a direction to permit access to the interior of said shell;

(g) a grate supported from said firewall in said forward portion of said shell;

(h) a tube in said shell that extends forwardly from an opening in the upper part of said firewall to a warm air discharge opening in said forward portion of said shell; and

(i) a damper adjustably supported from said firewall in said forward portion of said shell for regulating the draft to which fuel burning on said grate is subjected, which fuel as it burns heats said firewall to in turn heat said air in said confined space, with said heated air in said confined space rising to flow from said warm air discharge opening while cool air from a room in which said fireplace is situated is drawn into said confined space through said air passage to replace said heated air and in turn be heated for discharge into said room.

10. A fireplace as defined in claim 2, which further includes:

(k) an upright supported on said slab for removably holding fireplace implements in desired positions.

References Cited UNITED STATES PATENTS 2,028,088 1/1936 Davison et al 126-121 2,243,751 5/1941 Donley 12612l 2,970,590 2/1961 Fauser l26121 3,220,400 11/1965 Yager 126-121 X KETTERER, Primary Examiner, 

1. A PORTABLE PRE-CAST FIREPLACE, WHICH INCLUDES: (A) A BASE OF NONCOMBUSTIBLE MATERIAL THROUGH WHICH A HORIZONTAL COOL AIR PASSAGE EXTENDS THAT DEVELOPS AT THE REAR END THEREOF INTO AN UPWARDLY EXTENDING PASSAGE; (B) A RE-CAST SHELL OF LIGHTWEIGHT CONCRETE OF LOW HEAT CONDUCTIVITY AND HIGH TEMPERATURE RESISTANCE THAT RESTS ON SAID BASE, AND IN THE FORWARD PORTION OF WHICH SHELL A SYMMETRICAL FIREPLACE OPENING IS FORMED, WHITH THE UPPER PORTION OF SAID SHELL DEVELOPING INTO A TUBULAR NECK THAT CAN BE CONNECTED TO A FLUE PIPE; (C) A TRANSVERSELY POSITIONED METALLIC FIREWALL DISPOSED IN SAID SHELL THAT DIVIDES THE INTERIOR THEREOF INTO A REAR CONFINED SPACE THAT IS IN COMMUNICATION WITH SAID UPWARDLY EXTENDING PASSAGE IN SAID BASE AND AT LEAST ONE WARM AIR DISCHARGE OPENING FORMED IN THE UPPER REAR PORTION OF SAID SHELL,WITH THE FORWARD PORTION OF SAID DIVIDED SHELL BEING UTILIZED FOR THE CONSUMPTION OF FUEL; (D) TWO ABUTING DOORS THAT FIT WITHIN THE CONFINES OF SAID FIREPLACE OPENING; (E) MEANS FOR SO MOVABLY SUPPORTING EACH OF SAID DOORS THAT THEY CAN FIRST BE WITHDRAWN FROM SAID OPENING AND THEN PIVOTED IN A DIRECTION TO PERMIT ACCESS TO THE INTERIOR OF SAID SHELL; (F) A GRATE SUPPORTED FROM SAID FIREWALL IN SAID FORWARD PORTION OF SAID SHELL; AND (G) A DAMPER ADJUSTABLY SUPPORTED FROM SAID FIREWALL IN SAID FORWARD PORTION OF SAID SHELL FOR REGULATING THE DRAFT TO WHICH FUEL BURNING ON SAID GRATE IS SUBJECTED, WHICH BURNING FUEL HEATS SAID FIREWALL TO IN TURN HEAT SAID COOL AIR ENTERING SAID CONFINED SPACE FROM SAID PASSAGE,WITH THEIR AIR HEATED IN SAID CONFINED SPACE RISING TO PASS FROM SAID WARM AIR DISCHARGE OPENING, WITH SAID COOL AIR AS IT RISES AND IS HEATED IN SAID CONFINED SPACE SERVING TO ABSORB SUBSTANTIALLY ALL THE HEAT RADIATED THERETO BY SAID FIREWALL AND BY SO DOING PREVENTING ANY SUBSTANTIAL HEATING OF SAID SHELL REARWARDLY OF SAID FIREWALL. 